When a woman is going down on a man, right before he ejaculates he pushes down on the back of her head (or punches her in the back of the head) causing he to choke and cough thus shooting the semen out her nose. Like a dragon shooting flames or ice of it's nose.
See, Ice dragon or white dragon

When a guy is about to cum, he puts the tip of penis up to the opening of his partners nose( one or the other openings ), and as he ejaculates, the other person pulls it in through the nose, down to the back of the throat, and then finally, spits it back on to his penis.